The present invention relates to the field of parabolic antennas.
So far as the inventors are aware, the parabolic reflectors that are commonly used nowadays are made of structures that are either entirely metallic or least that are provided with metallization that provides the reflecting surface.
Such reflectors have indeed given good service. However they present the following features:
metallic losses;
reflection is not frequency selective;
poor appearance;
manufacture is not trivial; and
they deform with temperature.
Attempts have been made to implement reflecting structures, including parabolic reflectors, based on a stack of dielectric sheets (see document DE-A-3 601 553). Nevertheless, at present, attempts based on that type of technology have not given satisfaction.
An object of the present invention is to propose a novel parabolic antenna that enables the drawbacks of the prior art to be eliminated.
According to the present invention, this object is achieved by a reflector made up of n contiguous layers of dielectric material defined by n+1 surfaces having distinct parabolic equations and shaped to define a common electromagnetic focus.
According to an advantageous additional 30 characteristic of the present invention, each layer is a uniform piece of dielectric (plastic, ceramic, air, etc. . . . ) having a dielectric constant e that is greater than or equal to 1 and presenting low loss.
Such layers can either be stacked merely by being juxtaposed and held by external clamping, or else they can be stuck one to another.
All of the layers are preferably defined by a common outline.
The inventors have determined that such a reflector, when properly implemented, has the following properties:
it reflects electromagnetic energy and concentrates it on a focus;
it operates in the vicinity of a predetermined fixed frequency;
it does not reflect electromagnetic waves that do not correspond to its operating frequencies (the reflector thus performs a filtering function);
the working bandwidth depends on the materials selected and on the number of layers;
it can provide very low loss, even at very high frequencies; and
it is made entirely out of dielectric materials that are transparent to electromagnetic waves.